In the medical field, hollow microneedles have been developed for delivering drugs or withdrawal of bodily fluids across biological barriers, such as skin. A microneedle is a miniature needle with a penetration depth of about 50–150 μm. The microneedle is designed to penetrate the skin but not hit the nerves. An array of microneedles may be combined with an analyte measurement system to provide a minimally invasive fluid retrieval and analyte sensing system. In other fields, solid mironeedles are desirable as probles to sense electrical signals or to apply stimulation electrical signals, and hollow microneedles are useful as means for dispensing small volume of materials.
Methods for fabricating microneedles from silicon have been proposed. However, silicon microneedles require expensive processing steps. Furthermore, silicon is highly brittle and susceptible to fracturing during penetration. Alternatively, microneedles may be made from stainless steel and other metals. However, metal microneedles are subject to several disadvantages, one of which is the manufacturing complexities involved in metal processing steps such as grinding, deburring and cleaning. Therefore, there exists a need for a method of fabricating metal microneedles that is relatively simple and inexpensive.